Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$54.75	8.756%	$59.5439	$59.54	$59.55	$59.50
Purchase #2	$194.93	10.584%	$215.5614	$215.56	$215.55	$215.60
Purchase #3	$100.48	8.202%	$108.7214	$108.72	$108.70	$108.70
Purchase #4	$181.40	6.348%	$192.9153	$192.92	$192.90	$192.90
Purchase #5	$239.31	6.215%	$254.1831	$254.18	$254.20	$254.20
Purchase #6	$123.58	5.557%	$130.4473	$130.45	$130.45	$130.40
Purchase #7	$78.69	13.471%	$89.2903	$89.29	$89.30	$89.30
7 purchase totals =	$973.14		$1,050.6627	$1,050.66	$1,050.65	$1,050.60